PARALYSIS OF THE HIND EXTREMITIES. 749 



1. Disturbance in movement, distinguished : — 



(a) By loss of strength, and 



(b) By irregularity in movement. The animals show weakness, 



and rapidly become tired ; the hind limbs, though able to 



sustain the weight of the body, only slightly assist in 



forward progress, and, during walking, make irregular 



ataxic movements. 



Ataxia is a form of interference with movement arising from 



defective co-ordination. The proper innervation of the separate 



groups of muscles is interfered with, in consequence of which their 



contractions are not harmoniously combined. Single groups 



contract too much or too little, others too early or too late. 



In horses and dogs, such symptoms accompany incomplete 

 paraplegia. The hind-feet are lifted hesitatingly and incompletely 

 from the ground ; the toe may be dragged and gradually worn, or 

 the heels may first come in contact with the ground, the toe being 

 tilted at each step. In the next stage the foot is lifted suddenly 

 and to an abnormal height, is set down awkwardly and with a tapping 

 movement, and often describes a semicircle outwardly ; the feet 

 are placed crosswise over one another, while the hind-quarters roll 

 first to one side and then to the other (plaiting the legs). These 

 ataxic movements are particularly well seen when turning ; the 

 animal has difficulty in backing. 



2. Sensibility and reflex irritability are generally retained, the 

 latter may even be increased, causing exaggeration of the tendon 

 reflexes. In general the same remarks apply here as were made 

 in reference to complete paraplegia. 



3. Muscular atrophy. This is seldom seen in incomplete spinal 

 paralysis, or is confined to gradual atrophy of both sides in conse- 

 quence of inactivity. In one case Cadeac found the pectoral, 

 scapular, humeral, femoral and facial muscles soft, yellowish, 

 atrophied and degenerated. 



4. The paraplegia of dogs, due to disease of the spinal column, is 

 almost always associated with spastic contraction of the extensors, 

 and, according to Dexler, with anaesthesia of the testicle. 



The exceptional occurrence of atrophy in the spinal form of 

 incomplete paraplegia shows that the cause lies in front of the trophic 

 centre of the muscles, that is, in the posterior columns of the medulla, 

 as paralysis due to brain injury generally takes the form of 

 hemiplegia. 



The several causes of paraplegia incompleta spuria lie outside 

 the spinal cord or spinal column. They sometimes consist in fissuring 



